A cyclam-like macrocycle with an integrated push-pull chromophore selectively detects Cu²⁺ inclusion through both orange-to-yellow colour change and quenching of the green fluorescence.

In this paper we describe the electrochemical synthesis and characterization of new neutral manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead complexes with the ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine, H₄DAPTsz-Me. X-Ray structures of [Mn(H₂DAPTsz-Me)(EtOH)₂] 1, [Pb(H₂DAPTsz-Me)] 3 and [Zn(H₂DAPTsz-Me)]₂·EtOH·2H₂O 4, were also determined. In these complexes the ligand behaves as bis-deprotonated and SNNNS pentadentate. In the manganese complex the metal is heptacoordinated, in a distorted pentagonal-bipyramidal environment, with the N₃S₂ donor set of the ligand in the pentagonal girdle and two solvent molecules occupying the axial positions. In the lead complex 3 the metal is pentacoordinated, bound exclusively to the five donor atoms of the ligand, as a consequence of the existence of “inert pair effect”. The bishelical zinc complex 4 shows each zinc atom with different coordination geometry, one octahedrally six-coordinate while the other is distorted tetrahedrally four-coordinate.

The neutral dinuclear dihelicate [Cu₂(L)₂]·2CH₃CN (1) forms a unique 3D network in the solid state due to π-stacking interactions, which are responsible for intermolecular antiferromagnetic coupling between Cu(II) ions.

The copper complex of 2,6-bis(1-salicyloylhydrazonoethyl)pyridine, H₄daps, has been prepared by an electrochemical procedure and characterised by elemental analysis, IR, FAB mass spectroscopy, Λ_M, magnetic susceptibility measurements and EPR studies. The molecular structures of the ligand H₄daps (1) and its copper complex [Cu(H₂daps)(H₂O)]₂·2CH₃CN (3) have been determined by X-ray diffraction studies. The ligand shows in the solid state a syn-open conformation that allows it to act as a binucleating ligand, after a conformational change, as is shown by the study of the copper dihelicate 3. This compound contains the dianionic ligand [H₂daps]²⁻ in an anti-open conformation. The comparative study of this complex, with others previously reported, allows us to confirm that the conformational rearrangement undergone by H₄daps upon complexation depends strongly on the metal nature and its stereochemical preferences.